Anatomy of the Respiratory System Flashcards
The pulmonary arteries carry deoxygenated blood; True or False?
True
What are the different types of cells in the alveoli of the lung?
- Type I pneumocyte
- Type II pneumocyte
What are type I pneumocytes?
Simple squamous epithelium make up approximately 95-97% of the surface area of alveoli. They are thin which allows the rapid diffusion of gases
What is classed as the upper respiratory tract?
- Nasal cavity
- Mouth
- Pharynx
- Larynx
What is classed as the lower respiratory tract?
- Trachea
- Bronchi
- Left and right lung
What are type II pneumocytes, and what is their function?
Thicker cells than Type I pneumocytes. These cells:
- Synthesise surfactant
- Transport solutes (and thus fluid) out of the alveolar air space
How does the respiratory tract lining progress from the nasal cavity to the alveoli?
Pseudostratified ciliated columnar epithelium (upper and proximal lower resp. tract) to simple squamous epithelium (type I and II pneumocytes).
Why does the lung stick to the wall of the chest cavity?
Cohesive forces exerted by the fluid between the visceral and parietal pleura cause the lungs to “stick” to the thoracic cavity wall. The elastic recoil of the lungs constantly tries to pull the visceral pleura away from the parietal pleura, which is counteracted by the outward pull of the thoracic cage.
The stickiness is created subatmospheric pressure the is created by the parietal and visceral pleura pulling away from each other
.
What is the resting pressure of the pleural space?
-3 mmHg
What does the intrapleural pressure fall to on inspiration?
-6 mmHg on normal breathing
What is the intrapleural pressure relative to the alveolar pressure?
More negative - whenever alveolar pressure falls below atmospheric pressure, this pulls air into the lungs
What are the muscles used in inspiration?
- Diaphragm
- Scalenes
- External intercostal muscles
- Sternocleidomastoid
How to the external intercostal muscles help with inspiration?
Pull the ribs upwards and outwards
How do the scalenes help expand the chest?
Pull the ribs upwards and outwards
How do the internal intercostal muscles help with expiration?
Force rib cage downwards and pull ribs inwards
How do the abdominal muscles aid expiration?
Pulls lower rib cage inwards and reduces abdominal volume, which displaces abdominal viscera upwards, displacing thoracic cavity volume
How does the sternocleidomastoid muscle help with inspiration?
Pulls ribs upwards
How does surfactant reduce the amount of work needed to expand the lung?
Disrupts the cohesive forces between water molecules in alveolar fluid, thus decreasing the surface tension of alveolar fluid, and thereby reducing the pressure exerted on the centre of the alveoli
If there were no surfactant, the surface tension of small and large alveoli would be the same. Based on the LaPlace’s law, this would result in increased pressure within the smaller alveoli. This would lead to more work being needed to counteract the force of the pressure being exerted towards the centre of the alveolus.
Why is surfactant more effective in smaller alveoli?
Surfactant molecules are brought closer together, and therefore become more concentrated.
What are the different respiratory areas found in the brainstem?
- Cerebral cortex
- Pontine respiratory group
- Dorsal respiratory group
- Ventral respiratory group - including pre-botzinger and botzinger complex
- Nucleus retoambigualis
- Nucleus paraambigualis
- Nucleus ambiguous
What does the dorsal respiratory group control?
Muscles of inspiration
What nerves does the DRG send signals down to activate the muscles of inspiration?
- Phrenic nerve
- Intercostal nerves
What is the function of the pontine respiratory group?
Governs the activity of the medullary respiratory groups, integrating descending control of respiration from the CNS
What is the blood supply to the external nose?
Extensive arterial supply with multiple areas of anastomosis
- dorsal nasal artery (a terminal branch of the ophthalmic)
- external nasal artery (from the anterior ethmoidal)
- lateral nasal and septal branches of the facial artery
- superior labial branch of the facial artery
What is the venous drainage of the external nose?
Vens are collateral with the arteries, and drain into the pterygoid plexus, facial vein or cavernous sinus. Drainage into the saggital sinus is a normal anatomical variation.
What is the nervous supply for the external nose?
- external nasal nerve (the terminal part of the anterior ethmoidal)
- supratrochlear and infratrochlear nerves
- nasociliary nerve
- nasal branches of the infraorbital nerve
What are the 3 main areas of the nasal cavity?
- Vestibular area - lined by skin (extends 1cm into the cavity)
- Respiratory area - lined by respiratory mucous membrane with pseudostratified ciliated columnar epithelium. Contains the three concha which project into the cavity.
- Olfactory area - at the roof of the cavity (lower boundary is the superior conchae)
What is the blood supply to the nasal cavity?
- Sphenopalatine artery (terminal branch of the maxillary artery)
- Septal branch of the superior labial artery
- Ascending branch of the greater palatine artery
- All of these come together into an anastomosis in the lower anterior septum (Little’s area), which is called Kieselbach’s Plexus (where epistaxis commonly occurs)
What is the venous drainage of the nasal cavity?
- Veins are collateral with the arteries,
- Drainage is in multiple directions: pterygoid plexus via the sphenopalatine foramen, to the facial vein, to the ophthalmic vein and to the inferior cerebral vein.
What is the nervous supply of the nasal cavity?
- Vestibular area: infraorbital nerve
- Olfactory area: olfactory nerve
-
Respiratory area: lateral wall supplied by six nerves, septum by four nerves:
- Anterior ethmoidal nerve
- Anterior superior alveolar nerve
- Lateral posterior superior nasal branches from the pterygopalatine ganglion
- Posterior inferior nasal branches of the greater palatine nerve
- Olfactory nerve
- Medial posterior superior nasal nerve
- Nasopalatine nerve
What are the two main areas of the oral cavity?
- Vestibule: space between the teeth and lips/cheeks
- Oral cavity: space beyond the teeth
What is the blood supply of the oral cavity?
- greater palatine artery
- Tongue: lingual artery
What is the venous drainage of the oral cavity?
- Veins are collateral with the arteries,
- Drainage is to the pterygoid plexus and the pharyngeal plexus
